Publications

Looking for the γ-Ray Cascades of the KM3-230213A Neutrino Source

The KM3NeT collaboration recently announced the detection of an extremely high energy neutrino, with a best fit energy near 200 PeV. Such a source challenges our models of particle acceleration. Generically, such models will produce a bright GeV-TeV gamma-ray flux which is produced by the attenuation and re-emission of PeV gamma-rays that accommpanies the neutrino event. We utilize 16 years of Fermi-LAT data to search for such a signal, but do not find a convincing corresponding gamma-ray source. We utilize this model to set strong lower limits on the intergalactic magnetic field strength, which controls the evolution of the attenuated gamma-ray signal.

AGN-Driven Models for the Neutrino and Gamma-Ray Flux from NGC 1068

Recent observations by IceCube have found an extremely high neutrino flux from the Seyfert II Galaxy NGC 1068. These models are hard to reconcile with the relatively low gamma-ray flux from this galaxy, unless the neutrinos are produced in a region where the gamma-ray emission is strongly attenuated. However, gamma-ray attenuation produces lower-energy gamma-rays that should be obsrved by future telescopes at MeV energies. We study the parameter space which can simultaneously produce the bright neutrino emission and dim GeV gamma-ray emission, finding that this source must have extremely high magnetic and radiation fields near the central black hole. We forecast that future MeV telescopes will detect bright emission from this galaxy.

AGN Don't Produce the IceCube Neutrino Flux

Recent IceCube observations of the flaring blazar TXS 0506+056 have excited the community, potentially providing the first detection of a neutrino source. Additionally, the detection of neutrino emission from a blazar might indicate that blazars dominate the neutrino background. Here, however, we utilize detailed catalogs of optically and gamma-ray bright blazars, including a huge population of source that could potentially produce the diffuse IceCube neutrino emission. We find no evidence of neutrino hotspots associated with the known positions of blazars, and use this lack of correlation to rule out models where more than approximately 20% of the diffuse IceCube neutrino background is produced by blazar activity.

No Evidence of Neutrinos from the Fermi Bubbles

A recent analysis argued that the Fermi bubbles morphologically matches an excess in the morphology of IceCube neutrino events. We re-investigate this scenario, finding no evidence for such a scenario after the IceCube effective exposure is carefully considered. We note more generally that a combination of the IceCube neutrino flux and HAWC observations of TeV gamma-rays can constrain the leptonic or hardonic morphology of the bubbles, and show that there is presently no strong evidence for any IceCube neutrino flux from the Fermi bubbles region.

Full Publication List:

5. Looking for the γ-Ray Cascades of the KM3-230213A Neutrino Source
Milena Crnogorčević, Carlos Blanco, Tim Linden
Submitted to JCAP

4. On the Neutrino and Gamma-Ray Emission from NGC 1068
Carlos Blanco, Dan Hooper, Tim Linden, Elena Pinetti
To Be Submitted

3. Active Galactic Nuclei and the Origin of IceCube’s Diffuse Neutrino Flux
Dan Hooper, Tim Linden, Abby Vieregg
Journal of Cosmology and Astroparticle Physics 02 012

2. IceCube and HAWC Constraints on Very-High-Energy Emission from the Fermi Bubbles
Ke Fang, Meng Su, Tim Linden, Kohta Murase
Physical Review D 96 123007

1. Is the Ultra-High Energy Cosmic-Ray Excess Correlated with IceCube Neutrinos?
Ke Fang, Toshihiro Fujii, Tim Linden, Angela Olinto
The Astrophysical Journal, 794 126

Tim Linden

Assistant Professor, Stockholm University

linden@fysik.su.se

Neutrino Astronomy